Likely rough quartz crystal

The foreground specimen is translucent honey-brown to colorless, with a vitreous luster and irregular crystal faces; quartz has a trigonal crystal structure, Mohs hardness 7, no cleavage, and specific gravity about 2.65. The blue specimen behind it may be sodalite or another blue mineral, but its identity is not clear enough to determine visually.

Quartz crystallizes from silica-rich magma, hydrothermal fluids, and mineral-bearing cavities; it occurs in rocks of many ages. The photograph does not establish the specimens’ geological age or locality.

Quartz is used in glass, electronics, abrasives, and jewelry; attractive crystals are collected or cut as gemstones.

Quartz commonly forms six-sided prisms, though broken or weathered crystals can have irregular shapes. Iron staining can produce yellow-brown surface colors.

Look for hardness sufficient to scratch glass, lack of cleavage, and a glassy appearance; confirm with a scratch test only if damage is acceptable. Quartz is widespread worldwide, especially in veins, pegmatites, and geodes.